Fill Mate Liquid Sensor

Filling up your car or truck tank is easy enough – depress the handle until gasoline or diesel fuel reaches the proper height, and it cuts off automatically. Filling up a boat, however, works a bit differently and often lead to tiny spills at the gas station. This means the possibility of fuel getting into the water, which is obviously not a good situation. Actually preventing such micro-spills is a tough challenge, but creator Robert Werner (AKA rabbitcreek) has come up with a method that works with fuel, and could be used with other liquids as well.

The aptly named Fill Mate features an MS5803-14BA temperature and pressure sensor, normally used for altitude measurements, to determine fill levels. The sensor is pneumatically linked to the inside of the tank with a length of aquarium air line tubing, allowing it to first measure the pressure with no liquid present, then sense changes as the tank is filled. The device is controlled by an Adafruit ItsyBitsy board and a buzzer provides feedback when you’ve filled up.

The Fill Mate comes in a solar-charged version, which would be great for boat mounting, along with a non-solar version if that suits your needs better. It can be easily built for around $30 Naturally, you’ll want to take the appropriate precautions when dealing with anything flammable, so this is very much an at-your-own-risk project per Werner’s disclaimer.